The display characteristics of a liquid crystal display have been progressively improved in recent years. The viewing angle characteristics of a liquid crystal display are known to be notably improved by a retardation film displaced between a polarizing plate and a liquid crystal cell. For compensation of the viewing angle, it is preferable to control the optical characteristics of the retardation film used, specifically, the in-plane retardation (Re) and/or thickness direction retardation (Rth) within appropriate ranges depending on the display mode.
A method disclosed for controlling the Re and Rth of a retardation film involves addition of a retardation enhancer to a polymer film (see Japanese Patent Laid-Open No. 2004-109410). The retardation enhancer disclosed in this document is a compound capable of forming a molecular complex having a keto-enol tautomeric structure as a constituent element, and a typical example thereof is a compound containing a 1,3,5-triazine ring such as a guanamine skeleton. Other retardation enhancers are also disclosed, such as disk-shaped compounds and compounds having other 1,3,5-triazine ring-containing structures (see Japanese Patent Laid-Open No. 2001-166144 and Japanese Patent Laid-Open No. 2003-344655).    [Patent Literature 1] Japanese Patent Laid-Open No. 2004-109410    [Patent Literature 2] Japanese Patent Laid-Open No. 2001-166144    [Patent Literature 3] Japanese Patent Laid-Open No. 2003-344655